[QScrollArea] Scroll problem when adding widgets dynamically

[Naufrage7]

Hi,

I'm making a small network scanner. I have a QScrollArea and I add dynamically some widgets when new devices are found.

You can see the problem at https://youtu.be/1rm9ceZkIwY ( "mini jump" when a new widget is added inside the QScrollArea, so the adding is not smooth )

I'm using PySide 2 ( Python version of Qt ) but I don't think it comes from Python.

        self.scroll_area = QtWidgets.QScrollArea(self)
        self.scroll_area.setWidgetResizable(True)

        self.device_list_widget = DeviceListWidget() # Based on an QFrame, just contains QVBoxLayout ( layout contains widgets of course )
        self.scroll_area.setWidget(self.device_list_widget)

Is there any solution for me ?

If my English is not good, sorry I was born in France ... 😂
Thank's

[closx]

@Naufrage7 Hello my French friend, and oh god, I realized the "mini jump" so long after :D
If you wanna hear what I am thinking, it looks like a qt-based bug. Or you can try to fix the components better :P

[Naufrage7]

I think also. I have the impression that scroll area follow these steps :

• the widget is inserted without margin
• view is updated
• margin is calculated
• view updated

I will set all margins to 0 and check but I will have need these margin in production ...

[closx]

@Naufrage7 If you set the sizes of every component manually, and fix them, the problem will probably gone. But the application window (main window) should be fixed too. Otherwise, a change in main window size would screw the whole order tho :D Try and let us know!
Good work!

[SGaist]

Hi,

What version of PySide2 are you using ?
Can you provide a minimal complete example that shows that behavior ?

[Naufrage7]

Hi,

I'm using the version 5.12.4 of Pyside 2 version ( installed from pip ).

from PySide2 import QtCore, QtWidgets
from ARPRequestEmitter import ARPRequestEmitter
from ARPResponseReceiver import ARPResponseReceiver
from threading import Thread
from random import randint
import sys


class DeviceListWidget(QtWidgets.QFrame):

    def __init__(self, parent=None):
        super(DeviceListWidget, self).__init__(parent)

        self.vertical_layout = QtWidgets.QVBoxLayout()
        self.setLayout(self.vertical_layout)

        item_spacer = QtWidgets.QSpacerItem(0, 0, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
        self.vertical_layout.addItem(item_spacer)

    def add_device(self, ip, mac):
        widget = QtWidgets.QWidget()
        layout = QtWidgets.QVBoxLayout()
        label = QtWidgets.QLabel(ip)
        layout.addWidget(label)
        label = QtWidgets.QLabel(mac)
        layout.addWidget(label)
        widget.setLayout(layout)
        self.vertical_layout.insertWidget(0, widget)


class Dialog(QtWidgets.QDialog):

    def __init__(self):
        super(Dialog, self).__init__()

        self.resize(640, 480)

        self.horizontal_layout = QtWidgets.QHBoxLayout()
        self.setLayout(self.horizontal_layout)

        self.vertical_layout_left = QtWidgets.QVBoxLayout()
        self.horizontal_layout.addLayout(self.vertical_layout_left)

        self.vertical_layout_right = QtWidgets.QVBoxLayout()
        self.horizontal_layout.addLayout(self.vertical_layout_right)

        self.label_decoration_network = QtWidgets.QLabel("Réseau")
        self.vertical_layout_left.addWidget(self.label_decoration_network)

        self.form_network = QtWidgets.QFormLayout()
        self.vertical_layout_left.addLayout(self.form_network)

        self.label_network = QtWidgets.QLabel("192.168.178.0/24")
        self.form_network.addRow(QtWidgets.QLabel("Adresse"), self.label_network)

        self.label_gateway = QtWidgets.QLabel("192.168.178.1")
        self.form_network.addRow(QtWidgets.QLabel("Passerelle"), self.label_gateway)

        self.label_capacity = QtWidgets.QLabel("0 / 254")
        self.form_network.addRow(QtWidgets.QLabel("Capacité"), self.label_capacity)

        item_spacer = QtWidgets.QSpacerItem(0, 0, QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Expanding)
        self.vertical_layout_left.addItem(item_spacer)

        self.line_filter = QtWidgets.QLineEdit(self)
        self.line_filter.setPlaceholderText("Tapez ici pour filter les périphériques affichés")
        self.vertical_layout_right.addWidget(self.line_filter)

        self.scroll_area = QtWidgets.QScrollArea(self)
        self.scroll_area.setWidgetResizable(True)
        self.vertical_layout_right.addWidget(self.scroll_area)

        self.device_list_widget = DeviceListWidget()
        self.scroll_area.setWidget(self.device_list_widget)

        self.hosts = []

        # self.arp_receiver = ARPResponseReceiver('en0')
        # self.arp_receiver.response_received.connect(self.__arp_received__)
        # self.arp_receiver.start()

        # self.arp_emitter = ARPRequestEmitter('en0', '192.168.178.0/24')
        # self.arp_emitter.start()

        self.timer = QtCore.QTimer()
        self.timer.timeout.connect(self.__timeout__)
        self.timer.start(500)

    def __timeout__(self):
        self.__arp_received__(['192.168.178.' + str(randint(0, 256)), '@MAC'])

    def __arp_received__(self, host):
        if host not in self.hosts:
            self.hosts.append(host)
            self.label_capacity.setText(str(len(self.hosts)) + " / 254")
            self.device_list_widget.add_device(host[0], host[1])


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    dialog = Dialog()
    dialog.show()
    sys.exit(app.exec_())

I tested some combinations adding or removing margins and changing the size policy but I could not find solution.